There’s a lot written about electrical safety as it applies to infrared inspections. The danger of electric shock and exposure to arc flash hazards must be considered when inspecting electrical apparatus with thermography. What isn’t discussed nearly as often are the hazards associated with mechanical infrared inspections, of which there are many.

Roller Bearing

One area of concern is inspecting rotating equipment. Whether, its bearings, motors, couplings or belt drive components, special care should be taken when working around rotating assets. Even devices driven by fractional horsepower motors generate an enormous amount of torque and can cause serious injury if your clothing, hair, body parts or even the strap on your camera get caught in them.

In many facilities, couplings and belt drive components are guarded for safety purposes and as such may not be readily available for inspection. If removal of a guard is necessary for inspection purposes, it’s advisable to first de-energize the rotating device in question, if possible. Another option is to utilize a good thermal mirror (polished aluminum for example) and place it below or at an angle where you can view the component’s reflection. While temperature measurements will probably not be accurate, the qualitative image will tell you a great deal.

Thermography is also very useful for inspecting high temperature systems such as boilers, steam lines, and kilns. Special care should be taken in high temperature areas for a number of reasons. Thermal imaging cameras often have not-to-exceed operating temperatures, which can be easily encroached upon in high temperature areas. Additionally, the surfaces being inspected could be of sufficient temperature to cause serious burns if bodily contact is made.

Sometimes steam lines and even boiler skins are coated with a low emissivity material to reduce radiant heat loss, and the danger to personnel is that these surfaces can often feel like they aren’t very hot–even with your hand held as close as an inch away. Once contact is made however, radiation isn’t the mode of heat transfer any longer and severe burns can occur. Also of concern in high temperature areas is heat exhaustion. Exposure to high temperature areas should be limited to short periods of time with time in between to cool off and re-hydrate.

So please remember to be safe during mechanical inspections. Attention to detail and following proper inspection procedures can help you stay safe while you Think Thermally®.

Even in applications where qualitative analysis is utilized, most reports include temperatures. For comparison purposes it’s advisable to measure a point of comparison, or reference, for the anomalous finding. In electrical applications, we generally advise comparing an adjacent phase of the same apparatus under similar load and environmental conditions. For mechanical applications it may be a nearby similar asset under similar load/cycling in a similar environment. Another commonly used point of comparison is ambient temperature. Sadly, many thermographers, both novice and experienced, are using ambient temperature in different ways.

Ambient temperature is defined by McGraw-Hill Science and Technology Dictionary as “… the temperature of the surrounding medium, such as gas or liquid, which comes into contact with the apparatus.” Depending upon the application, ambient temperature for the object being inspected can vary quite widely from what the thermographer may consider as ambient. Thermographers often cite different sources for ambient– anywhere from the air temperature where they’re standing during the inspection, the temperature of the nearest measuring device (such as a thermostat), a nearby component, etc. So, where should you measure it?

In a substation for example the air temperature at ground level could be much different than a component 30 feet in the air around the corner of the structure. In distribution equipment, the ambient temperature where the thermographer is standing might be different than the inside of an electrical enclosure. The interior of the enclosure might be warmer, due to inherent temperature from operating components, or it could be cooler if there is forced convention from cooling fans or cabinet air conditioners. If panel covers are taken off a long time before the inspection occurs, ambient temperature could have changed drastically. In mechanical applications there can be variances too. Rotating equipment might be at, or near, air temperature because of convection, but there may also be boundary layers on surfaces where the air movement is reduced due to the geometry of the surface.

Be cognizant of the true operating environment of the devices or systems you are inspecting. If you’re reporting an electrical anomaly, measure ambient on a high emissive surface inside of the enclosure or in close physical proximity to your object of interest. Note if the environmental conditions are substantially similar or different. Carrying a pocket weather station on inspection routes is a good idea, which in addition to air temperature can provide you with relative humidity and air velocity, if those are factors that need consideration in your application. It can also be beneficial to document the measurement, the method used to take the data and where it was taken. This information is especially valuable when obtaining a baseline or trending over time.

Ambient may seem like a simple figure, but in some cases it can be anything but simple.

The punch line to the old joke, “How do you get to Carnegie Hall?” is three simple words, “Practice, practice, practice.” The same would hold true if there was a thermographic equivalent to Carnegie Hall. You’d get there with practice … lots of it!

Some folks who come to Level I infrared training, however, express that they have limited access to their infrared imager, or that they only do inspections a few times a year, and that when they take their camera out that they feel kind of rusty. The easy cure to feeling rusty with your infrared camera is more practice. What if you have limited access to the systems you’re going to be inspecting, how do you get your time in on the imager to keep your skills sharp?

The fact of the matter is that no matter where you aim your thermal imager, there are thermal patterns to be seen. You can get plenty of practice with items you normally would not inspect. Regular household items, wildlife in the park, pets, kids, all of these objects are opportunities to fine tune your imaging skills. Will your cat look the same in your imager as a motor control center starter? Of course it won’t, but taking a high quality image of Fluffy the Cat requires the same attention to detail and the same image optimization skills as imaging a motor starter.

Infrared image of Fluffy the Cat.

Infrared image of a motor starter.

ANY opportunity to image objects is a good chance to practice focusing sharply, adjusting the span and level, freezing and storing an image, and changing palettes. The more you work with your infrared imager, the more comfortable you’ll feel using it when it counts in the field. So, go out there and image your lawn mower, your bird bath or your dog. Practice makes perfect!

We have several customers that we visit and perform infrared scans for on a regular basis. Recently we were in a textile mill in a state where we’ve been performing inspecting for the past four years. The equipment list has remained virtually unchanged in the time we’ve been inspecting there. The only variances were during shutdowns for predictive maintenance actions that correspond to our visits.

There has been a trend occurring at this particular textile mill over the years that we first noticed last year. On our semi-annual visit last year we found only four thermal anomalies in the entire plant. For the scope of the job, that’s a pretty small number. On our second visit last year we found only three. Mind you, the three anomalies found on the second visit of last year weren’t repeats. They were three new problems, previously undetected. They were lower-grade issues found in control panels. No problems in the primary distribution equipment at all. On my most recent visit I was shocked to find no anomalies at all. Zero, zilch, none!

This is what could be termed as a great return on investment! The steady application of reliability testing revealed failures and initiated repair actions, and the effect over a four year period has been measureable. Once we first noticed the reduction in the number of items discovered in our inspection, we started asking questions of the maintenance folks that had hired us to do the work in the first place. In the four year period that we had been inspecting for them, they had seen an 11% improvement in unscheduled downtime. In the first half of this year they have had no equipment failures that resulted in lost production time.

Obviously a closer look would be preferred so we could more closely measure the impact of our inspection efforts. Unfortunately, this particular customer’s reliability program is in its infancy, and they’re not measuring all of the Key Performance Indicators (KPIs) that a more advanced program might.

The first inspection we performed for them four years ago yielded nearly 20 anomalies, many of which were in critical electrical distribution apparatus. The improvement in this case is fairly obvious, and a testament to the value of thermal imaging.

As a conscientious maintenance professional, you no doubt take pride in your equipment. As such, you take the proper actions to make sure your tools are in tip-top shape. Your camera is no different. You make sure to keep it secure in its case when you transport it, you protect it from dirt, moisture, harsh environments, and perform regular maintenance or calibration as needed. Part of you care regimen might be to clean the lens periodically. However, sometimes good intentions can yield negative results if you don’t take precaution when cleaning your camera lens.

Of course your camera lens will require cleaning from time to time, but it’s important that when you clean it that you clean it properly. In nearly every type of facility where infrared cameras are employed you can find safety glasses cleaning stations. While prepackaged lens wipes are convenient, and work well on safety glasses, arc flash face shields, and laptop screens, they are not intended for use on your camera lens.

Your thermal imager lens has special coatings that enhance the transmissivity of the lens material as well as mitigate other unwanted wavelengths. With improper cleaning, the coatings can become damaged. Make sure that you only use the manufacturer’s recommend cleaning solution when cleaning your lens, and make sure you only do it as often as is needed. Repeated cleanings, even with the right solution and wipes, can cause wear of the lens coating, shortening the useful life of your lens. Protect your camera, keep it clean, but do it right!

A new generation of tools with next generation performance

This trio of new Fluke infrared cameras is equipped with LaserSharp™Auto Focus. For consistently in-focus images. EVERY.SINGLE.TIME.

Every infrared camera user knows that without an in-focus image temperature measurements may not be accurate and it’s much easier to miss a problem. LaserSharp™Auto Focus tells you exactly where you are focusing. This is point-and-shoot-and-get- it-right every single time performance.

The choices in the infrared camera market extend beyond just camera features like resolution, Bluetooth capability and storage card size. These days the market of infrared camera accessories is a separate category in its own right. Additional lenses are among the most popular choices for addition to your basic thermal imaging camera platform, but does everyone need additional lens choices?

Infrared cameras come with a standard lens that is designed to provide a field of view that allows inspection of surfaces at a moderate distance. Obviously, when you close your distance to a target your perspective changes, often to the point that you’re unable to view the entire surface without changing positions or scanning back and forth. Sometimes we are able to adjust our position relative to our area of interest to make up for the limitations of our standard optics. It’s when we can’t adjust our position that these additional lens options are worth their weight in gold.

If I’m tasked with inspecting something like overhead bus duct, or pole mounted electrical apparatus, my field of view may require me to get closer to my target to even see the component I’m viewing. Another option is a telephoto lens. A telephoto lens optically narrows your field of view, the effect of which is to bring the object you’re viewing “closer” to the camera, or magnifying the image. If a significant portion of your inspection targets are at a great distance from where you’re able to stand and view them, then a telephoto lens is likely worth having.

On the other side of the coin are instances when our target or area of interest is too close to our position during the inspection and we can’t view the full scene as desired. This can happen in electrical rooms, mechanical areas, and in building inspections. These are excellent opportunities to employ a wide angle lens. The wide angle lens does the opposite of a telephoto; it optically widens your field of view, effectively pushing your target “away” from you, or reducing the image.

In short, what makes optional lenses right for you is the applicability to your type of inspection. If you can easily move closer or farther away, the need for an extra lens is not great. But if you need to magnify or reduce the size of the target you are viewing, optional lenses will help you get the best thermogram possible.

One of the most widely used features added to cameras in recent years is the “auto” button or “auto range” setting. In “auto mode,” or with the touch of the “auto button,” your imager will automatically adjust the level and span setting to account for the warmest and coolest items in the field of view at that time. Some cameras have a button that is a one-time adjustment, and others have a setting that continuously re-adjusts as the camera pans around and items in the field of view change.

It is a very useful feature for sure, particularly when your inspection location changes from one ambient extreme to another. Remember, the auto feature adjusts the level and span settings to account for the warmest and coolest objects (and everything in between) in the field of view of the camera at that time. If there are extreme temperature variances in the field of view when auto is selected, and at the same time somewhere between those extremes is a thermal anomaly, the auto feature may very well mask it. See Figures One and Two below.

Figure Two

Figure One

These two images are actually the same. In Figure One, the “auto” range was selected. As you can see, the contrast in Figure One is much wider due to the temperature of the thermal foreground of the field of view, which is the very cold morning sky. The warmest surface in each image is clearly the two noted anomalies. Had the thermographer relied solely on the auto feature when taking the above image, the switch anomalies may very well have been missed.

The auto range function must be used with care. In the back of your mind, need to have the thought that the image you see may not be at the optimum level and span settings to detect every possible problem. Manual optimization is still often quite necessary in order to detect lower grade anomalies.

Awareness of the limitations of this feature is the key to success in its use. Use it with care, and it can be your best friend. Use it frivolously and it could turn into your worst enemy.

Roof moisture inspections are one of those applications of infrared thermography that many in the industry have heard of, but not so many have attempted. It’s kind of a niche application, really. In my decade or so of experience in this industry, I’ve only had the opportunity to be involved in a handful of these types of inspections. Each one was unique, and each presented its own set of challenges.

The ASTM C1153, Standard Practice for Location of Wet Insulation in Roofing Systems Using Infrared Imaging is the guiding document for these types of inspections. It lists the conditions that have to be met in order for an attempt at a roof moisture inspection to be successful. Roof moisture inspections are really as much an art as they are a science. The standards suggest beginning your inspection an hour or two after sunset, after a sunny day. How long precisely it takes for a pattern to emerge is dependent upon many factors. Roof construction, weather conditions, camera resolution, lots of things. There’s no hard, fast rule. If there’s ballast on the roof, that impacts both what you see as well as how soon you see it. Also, the patterns often can be obscure, so it takes an experienced eye to pick out some of the lower magnitude anomalies.

What does the newly minted thermographer do then? It’s a good idea to spend some time perfecting the inspection process. If you can, try to tag along with a more experienced thermographer on your first few roof inspections. That’s a good idea with any of the applications really. Try to keep in mind that mastering an art takes time and give yourself plenty of opportunity to practice.